Need more storage for my SSD Gaming Space!

I have two Sandisk Extreme Pro 960GB (2TB) in RAID 0, and I'm wanting extra storage space for gaming apps, such as my Steam games, because I don't have enough space etc..
My question is: If I reformat the two Sandisks, could I add an PCI E ssd for extra space, for windows 10 and other apps and use the two Sandisks in RAID 0 for gaming or is there a better alternative?

I have 2 ssd on my games rig , I use c for the op sys and anything that you cant choose where to install and d drive for all steam and none steam games , when you reinstall steam client you must use the same user name , password etc or you wont get your games list back to re-install them. when installing steam choose existing user.

you must have a hell of a lot of stuff you don't use if you are thinking of getting another ssd , rather than buy another drive I would seriously consider having a clear out.

a pal of mine had 2 massive hard drives almost full just so he could show everyone how much stuff he got , then he wondered why his pc was slow. have you fallen into the same trap ( no offence meant ) , seriously have a clear out of stuff you know you don't need or hardly ever use.